Alberta E coli outbreak tied to milk shakes

May 13, 2005 (CIDRAP News)  Sixteen people have fallen sick and one is hospitalized with Escherichia coli O157:H7, most of them after drinking milk shakes at a popular drive-in restaurant in Calgary, Alta.

The Calgary Health Region traced the outbreak to a longtime employee of Peters' Drive-In, according to the Calgary Herald. The employee reportedly came to work despite being ill. She made a marshmallow milk shake mix that was served at Peters' from Apr 22 to 26, the Canadian Broadcasting Corporation (CBC) reported on May 10.

Fourteen of the 16 people identified in the outbreak had consumed marshmallow milk shakes, Judy MacDonald, MD, MCM, of Calgary Health Region told CIDRAP News today. MacDonald is deputy medical officer of health working on communicable disease control for the agency.

The CBC reported that three people were hospitalized briefly. A fourth, a 15-year-old named Sara Burgess, had a marshmallow shake on Apr 24, the Herald reported. The next day, she began vomiting and was hospitalized. She developed hemolytic uremic syndrome (HUS) and has been receiving dialysis at Alberta Children's Hospital because of kidney failure. She remained in fair to serious condition today, according to MacDonald.

MacDonald said its too soon to rule out the possibility of more cases.

The worker who made the milk shakes had the first case identified in the outbreak, said MacDonald. She was symptomatic before Apr 22 and continued to work until she was found to have a possible case of E coli on Apr 25.

The next week, on May 2 and 3, lab tests showed several more E coli cases, MacDonald said. Because a food worker had already been diagnosed, investigators quickly focused on the drive-in and found links among 15 cases. One case has not been linked to the drive-in, MacDonald said.

Using pulsed-field gel electrophoresis (PFGE), authorities have been able to confirm that the same strain of E coli infected at least 9 of the 16 people, MacDonald reported.

She said the outbreak carries an important lesson about food safety: although E coli infections are usually associated with eating undercooked ground beef, the pathogen can get into other foods if they are handled by infected people. Some of those who fell ill in this outbreak are vegetarians, she added.

Dr. Glen Armstrong, head of infectious diseases at the University of Calgary, told the CBC that foodservice workers should stay home if they're feeling ill.

The drive-in was temporarily closed, but it has been cleaned and reopened, the Toronto Globe and Mail newspaper reported on May 7.